The Blind Assassin features three embedded storylines. Between spring 1998 and May 1999, Iris Chase Griffen reflects on her life and family history while writing a manuscript. Iris is in her eighties and lives in the small Ontario town of Port Ticonderoga. She has no family left alive: her sister Laura, her husband Richard, and her daughter Aimee have all predeceased her. Iris does have a granddaughter named Sabrina, but the two of them are not close. Iris is still independent but relies on help from Myra, a local shop owner. Myra has a deep attachment to Iris because her own mother, Reenie, worked for the Chase family and cared for Iris and Laura when the girls were children. The narrative alternates between Iris’s present-day experiences as an elderly woman and her memories of her childhood and early life.
Iris’s narrative is interspersed with excerpts from a novel called The Blind Assassin, published in 1947. Iris’s younger sister Laura died in a car accident in 1945, and many people believe the death was a suicide. After Laura’s death, her manuscript for The Blind Assassin was found, and her novel was published posthumously. Laura’s novel describes a series of encounters between an unnamed man and an unnamed woman who are having an affair. It eventually becomes clear that the woman is wealthy, while the man is some sort of fugitive. When they meet, the man tells the woman an ongoing story about a distant planet called Zycron. The content of this novel within a novel implies that Laura may have had an affair with a working-class man with radical political opinions.
Iris and Laura Chase are born in 1917 and 1920, respectively, into a wealthy manufacturing family. Their mother dies young, and their father, Norval, is a distant man. By the 1930s, the Great Depression is putting a strain on the Chase business and stoking fears about Communism and workers’ uprisings. Norval begins to cautiously forge an alliance with a former business rival, a Toronto manufacturing tycoon named Richard Griffen. In September 1934, Laura befriends a mysterious young man named Alex Thomas. Alex seems to be a drifter with leftist political opinions. In the following months, he and Laura continue to meet as friends.
In December 1934, rioting breaks out in the town after a lockout at the Chase factory. Alex Thomas is accused of instigating the violence, and a warrant is put out for his arrest. Laura hides Alex in the house, and Iris ends up helping her sister. As Iris spends more time with Alex, an attraction develops between them, and he eventually kisses her. However, for Alex’s safety, it is necessary that he leave the house and make his escape from the town in January. In the next few months, Iris’s father makes it clear that he has brokered a deal with Richard Griffen to rescue the declining fortunes of the business and that the deal includes the condition that Iris and Richard marry. Iris marries Richard in May 1935, and the couple sets off to honeymoon in Europe.
Iris quickly realizes that her marriage is going to be unhappy, as Richard is cold and distant, and his sister Winifred dominates Iris. When the couple returns from their honeymoon in August 1935, Iris is horrified to learn that her father died shortly after they left, and Richard has concealed the news from her. Norval Chase drank himself to death after learning that Richard had gone back on their deal, and the Chase factories were going to be shut down. Iris is now trapped in an unhappy marriage, living in a grand mansion in Toronto. Laura moves in with her sister and brother-in-law but is rebellious and unhappy. In the autumn of 1935, both sisters separately encounter Alex on the streets of Toronto. Iris is shocked when, in February 1937, Winifred and Richard inform her that Laura has had a mental breakdown and been institutionalized. They claim that Laura is suffering delusions, including the idea that she is pregnant.
Iris gives birth to a daughter, Aimee, in April 1937 and loses touch with Laura after Laura is released from the clinic a few months later. Meanwhile, the narrative of The Blind Assassin reveals that the unnamed man ends the affair to go and join the Spanish resistance and then also goes to fight in World War II. The woman eventually receives a telegram informing her that he has been killed. In 1945, after World War II ends, Laura returns to Toronto and contacts her sister. She explains that she was indeed pregnant in the winter of 1937 and that Richard and Winifred had her institutionalized so that she would undergo an abortion and avoid a scandal. Iris assumes that Alex Thomas was the father of Laura’s child, especially since Laura seems to be hoping that she and Alex will reunite now that the war is over. Jealous, Iris tells her sister that Alex has been killed and that she and Alex were lovers in 1935-36. It is strongly implied, and later confirmed, that Alex is the true father of Iris’s daughter.
Within a day of this conversation, Laura dies in the car accident. Iris begins investigating and realizes that she is wrong. Richard had been coercing Laura into having sex with him by telling her that if she didn’t, he would turn Alex over to the authorities. Richard got Laura pregnant and then had her institutionalized to cover it up. Outraged, Iris leaves her husband and moves back to Port Ticonderoga to live with her young daughter. After the publication of The Blind Assassin stirs up interest in Laura’s life, it seems like Richard’s behavior is going to be revealed, and he kills himself to avoid the shame and scandal. Winifred retaliates by taking Aimee away from Iris. As a result, Iris always had a distant relationship with Aimee and Aimee’s daughter, Sabrina. Iris has lived a mostly lonely life, and with her death now approaching, she finally tells her full story for the first time so that Sabrina will understand the family history. Iris also reveals that she herself wrote The Blind Assassin, drawing on her memories of her affair with Alex and publishing it under Laura’s name.